Sheet guiding device for sheet feeders

ABSTRACT

A sheet-guiding device in a feed region of a sheet-processing machine includes a suction head settable to a format length of a sheet and flexible sheet-guiding elements disposed above a sheet conveying plane. The sheet-guiding elements have a constant length, are disposed so as to be stationary and are deflectable by a positional change of the suction head.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2005 046 685.0, filed Sep. 29, 2005; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sheet-guiding device for a feeding region of a sheet-processing machine, particularly a printing press.

When feeding sheets to sheet-processing machines, it is customary to employ a suction conveying device which includes lifting and/or dragging suckers. The uppermost sheet is separated from a sheet pile or stack by having the lifting suckers, in a lower position thereof, apply suction to the sheet, and then raising the lifting suckers. While the sheet is disposed in the raised position, blown air is guided under the sheet by separating blowers from the rear or trailing edge of the pile or stack, in order to assist in the separation of the sheet from the pile or stack and in the raising of the sheet, while lateral loosening blowers, in order to maintain the air pressure, continuously blow air against the lateral edges of the pile or stack in the leading section of the sheet. When the lifting suckers have reached the highest position thereof, horizontally reciprocating conveying suckers (dragging suckers) take over the sheet from the lifting suckers by applying suction to the sheet, and the suction air at the lifting suckers is switched off. Subsequently, the conveying suckers transport the sheet by performing a horizontal movement in the direction of the sheet-processing machine, so that the leading section of the sheet arrives at a transfer point at sheet transport devices of the downstream disposed sheet-processing machine, for example transport belts guided over a feed table. The take-over by the sheet transport device of the sheet-processing machine is effected by cyclical lowering of intermittently operated rollers, due to which the sheet is pressed onto the revolving or circulating transport belts. Simultaneously with the lowering of the intermittently operated rollers, the supply of suction air to the conveying suckers is interrupted and the conveying suckers are moved into the rear position thereof in the sheet conveying direction. Since the sheet is moved on the transport path by the rear loosening blowers, an increasing amount of air passes onto the upper side of the sheet, which results in a fluttering movement of the sheet. The stable and reliable transport of the raised sheet, particularly in the region of the leading sheet region, is thereby endangered on a prescribed transport path to the sheet-processing machine and, accordingly, the arrival of the sheet at the transfer point in synchronism with the machine cycle of the sheet-processing machine is endangered. Sheet-guiding devices are installed above the sheet conveying path in order to solve that problem.

A sheet-guiding device of that general type has become known heretofore from German Published, Non-prosecuted Patent Application DE 17 86 232 A1, corresponding to U.S. Pat. No. 3,482,833, wherein, in a feeding region of a sheet feeding device, a sheet is guided at the upper side thereof on a sheet conveying path over a sheet pile or stack by a plurality of horizontally disposed telescopically extensible sheet-guiding rods. The telescopic rods extend horizontally in one plane from a crossmember which is disposed behind a suction head in the sheet transport direction transversely with respect to the sheet transport direction and is connected to the suction head above the sheet pile or stack as far as a transfer point to a feed table of a printing press. The afore-mentioned sheet-guiding rods can be telescoped or pressed together upon the occurrence of a format-dependent adjustment of the suction head, respectively in and counter to the sheet transport direction. Stepwise extending sections are formed by the tubular sections of the sheet-guiding rods. The guiding elements are substantially dimensionally stable. A considerable disadvantage is that the sheet-guiding elements must be serviced or maintained in order to preserve the functional reliability thereof, because the telescopic rods are subject to increasing wear by contamination and abrasion.

It has become known heretofore from German Patent DE 195 37 284 C1, corresponding to U.S. Pat. No. 5,863,037, to employ respective elastic and expansible guiding belts which experience a longitudinal expansion in accordance with the displacement path of the suction head and are respectively wound or unwound by suitably provided winding elements.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a sheet-guiding device for guiding sheets reliably and without damage in the feed region of sheet-processing machines, particularly printing presses, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which is adjustable both to the longitudinal format of the sheet and the transverse format of the sheet.

With the foregoing and other objects in view, there is provided, in accordance with the invention, a sheet-guiding device in a feed region of a sheet-processing machine. The sheet-guiding device includes a suction head settable to the format length of a sheet. Flexible sheet-guiding elements are disposed above a sheet conveying plane. The sheet-guiding elements have a constant length and are disposed so as to be stationary, as well as to be deflectable by a positional change of the suction head.

In accordance with another feature of the invention, the sheet-guiding device further includes deflector guide elements for deflecting the sheet-guiding elements out of a set guide plane.

In accordance with a further feature of the invention, the sheet-guiding device further includes a first stationary crossmember. The sheet-guiding elements have a first end with which the sheet-guiding elements are disposed on the first stationary crossmember.

In accordance with an added feature of the invention, the sheet-guiding device further includes a second stationary crossmember. The sheet-guiding elements have a second end with which the sheet-guiding elements are disposed on the second stationary crossmember.

In accordance with an additional feature of the invention, the sheet-guiding device further includes axially displaceable and vertically adjustable holding devices by which the sheet-guiding elements are disposed on the second crossmember.

In accordance with yet another feature of the invention, the sheet-guiding device further includes a spring force-loaded tensioning roller for tensioning the sheet-guiding elements.

In accordance with a concomitant feature of the invention, the sheet-processing machine is a rotary press.

An advantage of the invention is that the sheet-guiding elements are adjustable in terms of format not only in the longitudinal direction of the sheet but also in the transverse direction of the sheet, so that the lateral format adjustment of devices, such as lateral pile or stack stops or lateral loosening blowers, for example, is not impeded by the sheet-guiding device, and sheet guidance over the entire sheet width nevertheless occurs.

A further advantage of the invention is that stepless or infinitely variable guiding devices having low friction are provided.

In addition, the sheet-guiding elements according to the invention afford the advantage that they require extremely low maintenance, because strong or thick cable or rope material exhibiting correspondingly low wear can be used due to obtuse deflection angles for the belt material. Format differences from the greatest possible format to the smallest possible format in the longitudinal direction of the paper do not have to be compensated for at the guiding cords, because the latter do not have a fixed point at the suction head, but rather are only deflected.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a sheet-guiding device for sheet feeders, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, side-elevational view of a sheet-fed rotary printing press illustrating the present invention;

FIG. 2 is an enlarged, fragmentary, side-elevational view of FIG. 1 showing a feeder of the printing press with a sheet-guiding system disposed above a sheet pile or stack;

FIG. 3 is a top-plan view of the sheet pile or stack with sheet-guiding elements disposed thereabove; and

FIG. 4 is a view similar to FIG. 2 showing an alternative embodiment for guiding the sheet-guiding elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawings in detail and first, particularly, to FIGS. 1 and 2 thereof, there is seen a sheet-processing machine, for example a printing press 1, having a sheet feeder 2, at least one printing unit 3 or 4 and a delivery 6. Sheets 7 are removed from a sheet pile or stack 8 and stream-fed singly or in an overlapping or shingled manner over a feed table 9 to a sheet-feeding device 5 which transfers the sheets 7 to the printing units 3 and 4 in an accelerated manner. The printing units 3 and 4, in a conventional manner, each include a respective plate cylinder 11, 12. The respective plate cylinders 11, 12 have respective devices 13, 14 for fastening flexible printing plates thereon. Moreover, each plate cylinder 11, 12 has a device 16, 17 assigned thereto for semi-automatically or fully automatically changing printing plates.

The sheet pile or stack 8 lies on a controllably liftable pile or stack board 10. Removal of the sheets 7 from the upper side of the sheet pile or stack 8 is effected by a so-called suction head 18 which has, among others, a number of lifting and dragging suckers 19, 21 for singling or separating the sheets 7. Moreover, blowing devices 22 are provided for loosening the upper sheet layers, and sensing or feeling elements 23 are provided for tracking or readjusting the stack or pile 8. A number of lateral and rear stops 24 are provided for aligning the sheet pile or stack 8, particularly the upper sheets 7 of the sheet pile or stack 8.

The suction head 18 is disposed in the rear region above the sheet pile or stack 8 and is mounted so as to be displaceable respectively in and counter to the sheet transport direction for format matching or adjustment. Provided on a common elevation level between the suction head 18 and the upper side of the sheet pile or stack 8 are a number of flexible sheet-guiding elements 26, for example in the form of cables, cords, belts and so forth, for ensuring that a sheet subjected to blown or blast air from the blowing or blast devices 22 cannot leave the provided transport path in an upward direction. The sheet-guiding elements 26 are fastened at a first end 27 thereof to a first crossmember 28, which is disposed in front or upstream of the sheet pile or stack 8 in the sheet transport direction, and are fastened at a second end 29 thereof to a second crossmember 31 which is disposed behind or downstream of the sheet pile or stack 8.

A respective sheet-guiding element 26 partly wraps around a spring-loaded tensioning roller 32 disposed on the rear crossmember 28. Two deflection rollers 33, 34 per sheet-guiding element 26 are fastened to levers 35, 40 and are disposed on the suction head 18 in a downwardly-directed manner, so that the sheet-guiding elements 26 are guided below and laterally around the suction head 18. The second end 29 of each sheet-guiding element 26 is disposed on the second crossmember 31 by a vertically adjustable and axially displaceable holding device 36. As is seen in FIGS. 2 and 3, the holding device 36 and the deflection rollers 33, 34 are preferably disposed, with respect to the height or elevation thereof, in such a way that the sheet-guiding elements 26 lie approximately in a common guide plane E approximately respectively parallel to the upper side of the sheet pile or stack 8 and a conveying plane.

If the suction head 18 is displaced in the sheet transport direction, i.e., in the direction of the second crossmember 31, when small format lengths are processed, a smaller geometric overall length of the sheet-guiding elements 26 of constant length is necessary. However, in order to be able to hold the sheet-guiding elements 26 in a constantly tensioned manner, a small deflection of the sheet-guiding elements 26 is produced by the tensioning roller 32.

In a second embodiment according to FIG. 4, the first deflection roller 33 of the first embodiment of FIG. 2 is replaced by a combination of two deflection rollers 41 and 42, which are wrapped around in an S-shape. One deflection roller 42 is disposed on a spring-loaded lever 43, while the other deflection roller 41 is disposed in a stationary manner on the suction head 18. Due to this guidance of the sheet-guiding elements 26, a displacement path of the suction head 18 does not have to be compensated for.

In the FIG. 4 embodiment as well, the suction head 18 is disposed in the rear region above the sheet pile or stack 8 and is mounted so as to be respectively displaceable in and counter to the sheet transport direction for format matching or adjustment. Provided on an elevation level between the suction head 18 and the upper side of the sheet pile or stack 8 are a number of flexible sheet-guiding elements 26, for example in the form of cables, cords, belts and so forth, which ensure that a sheet 7 subjected to the blowing or blast devices cannot leave the provided transport path in an upward direction. The sheet-guiding elements 26 are fastened at the first end 27 thereof to the first crossmember 28 which is disposed in front or upstream of the sheet pile or stack 8 in the sheet transport direction, and are fastened at the second end 29 thereof to a second crossmember 31 disposed behind or downstream of the sheet pile or stack 8. 

1. In a sheet-processing machine having a feed region, a sheet-guiding device disposed in the feed region, the sheet-guiding device comprising: a suction head to be set to a format length of a sheet defining a sheet conveying plane; and flexible sheet-guiding elements disposed above said sheet conveying plane, said sheet-guiding elements having a constant length, being stationary and being deflected by a positional change of said suction head.
 2. The sheet-guiding device according to claim 1, which further comprises guide elements for deflecting said sheet-guiding elements out of a guide plane.
 3. The sheet-guiding device according to claim 1, which further comprises a first stationary crossmember, said sheet-guiding elements having a first end disposed on said first stationary crossmember.
 4. The sheet-guiding device according to claim 3, which further comprises a second stationary crossmember, said sheet-guiding elements having a second end disposed on said second stationary crossmember.
 5. The sheet-guiding device according to claim 4, which further comprises axially displaceable and vertically adjustable holding devices holding said sheet-guiding elements on said second crossmember.
 6. The sheet-guiding device according to claim 1, which further comprises a spring force-loaded tensioning roller for tensioning said sheet-guiding elements.
 7. The sheet-guiding device according to claim 1, wherein the sheet-processing machine is a rotary printing press. 